The present invention relates to a gear change, and in particular to a gear change for an industrial vehicle.
Gear changes are known in which the coupling of the various gears is carried out by sliding sleeves controlled by fluid actuators via respective rods and forks. The actuation of these actuators is generally obtained by supplying electrical signals to a group of electrovalves which generate drive signals for power valves adapted selectively to supply the chambers of the actuators with the operating fluid. The electrical actuation signals may be generated by an electronic unit in response to enabling signals received from manually actuated transducers, for instance associated with a gear lever of conventional type, and/or automatically following processing of signals representing the operating conditions of the vehicle.
Gear changes for industrial vehicles are also generally provided with several stages in cascade, for instance a divider or "splitter" stage with two ratios, a main stage with three or four ratios plus reverse and a rank reducer with two ratios. Each of these stages is controlled by a respective actuator or, in the case of the main stage, by two actuators with axes at right angles to one another so as to allow the selection of the gear to be coupled by rotation of the control rod and coupling of the gear by translation of this rod.
Known gear changes of the type outlined above have certain drawbacks.
In particular, the various control members (actuators, electrovalves, power valves) are generally disposed in different positions; for instance, the valves are generally separated from the actuators and the latter are secured to the exterior or the interior of the gear box on different portions thereof.
The assembly of the various members is therefore complex and costly; the electrical and hydraulic cables are complicated; subsequent action in the event of malfunction is problematic; the arrangement of the various portions must be studied case by case and makes it impossible to standardize the controls for different versions of the gear change or for different gear changes or to vary the degree of automation of the gear change after initial installation.
The actuators are generally offset with respect to the control rods and are connected to these rods by transmission members which subject these rods to bending stresses.